@socket.io/bun-engine

A highly efficient, Bun-powered engine for Socket.IO, designed to enhance real-time communication performance.

This package provides a custom engine for Socket.IO that leverages the speed and scalability of Bun to handle WebSocket connections seamlessly.

Reference: https://socket.io/

Table of contents

• How to use
  • With Bun's HTTP server
  • With Hono
• Options
  • path
  • pingTimeout
  • pingInterval
  • upgradeTimeout
  • maxHttpBufferSize
  • allowRequest
  • cors
  • editHandshakeHeaders
  • editResponseHeaders
• License

How to use

With Bun's HTTP server

import { Server as Engine } from "@socket.io/bun-engine";
import { Server } from "socket.io";

const io = new Server();

const engine = new Engine({
  path: "/socket.io/",
});

io.bind(engine);

io.on("connection", (socket) => {
  // ...
});

export default {
  port: 3000,
  idleTimeout: 30, // must be greater than the "pingInterval" option of the engine, which defaults to 25 seconds

  ...engine.handler(),
};

With Hono

import { Server as Engine } from "@socket.io/bun-engine";
import { Server } from "socket.io";
import { Hono } from "hono";

const io = new Server();

const engine = new Engine();

io.bind(engine);

io.on("connection", (socket) => {
  // ...
});

const app = new Hono();

const { websocket } = engine.handler();

export default {
  port: 3000,
  idleTimeout: 30, // must be greater than the "pingInterval" option of the engine, which defaults to 25 seconds

  fetch(req, server) {
    const url = new URL(req.url);

    if (url.pathname === "/socket.io/") {
      return engine.handleRequest(req, server);
    } else {
      return app.fetch(req, server);
    }
  },

  websocket
}

Reference: https://hono.dev/docs/

Options

path

Default value: /engine.io/

It is the name of the path that is captured on the server side.

Caution! The server and the client values must match (unless you are using a path-rewriting proxy in between).

Example:

const engine = new Server(httpServer, {
  path: "/my-custom-path/",
});

pingTimeout

Default value: 20000

This value is used in the heartbeat mechanism, which periodically checks if the connection is still alive between the server and the client.

The server sends a ping, and if the client does not answer with a pong within pingTimeout ms, the server considers that the connection is closed.

Similarly, if the client does not receive a ping from the server within pingInterval + pingTimeout ms, the client also considers that the connection is closed.

pingInterval

Default value: 25000

See pingTimeout for more explanation.

upgradeTimeout

Default value: 10000

This is the delay in milliseconds before an uncompleted transport upgrade is cancelled.

maxHttpBufferSize

Default value: 1e6 (1 MB)

This defines how many bytes a single message can be, before closing the socket. You may increase or decrease this value depending on your needs.

allowRequest

Default value: -

A function that receives a given handshake or upgrade request as its first parameter, and can decide whether to continue or not.

Example:

const engine = new Server({
  allowRequest: (req, connInfo) => {
    return Promise.reject("thou shall not pass");
  },
});

cors

Default value: -

A set of options related to Cross-Origin Resource Sharing (CORS).

Example:

const engine = new Server({
  cors: {
    origin: ["https://example.com"],
    allowedHeaders: ["my-header"],
    credentials: true,
  },
});

editHandshakeHeaders

Default value: -

A function that allows to edit the response headers of the handshake request.

Example:

const engine = new Server({
  editHandshakeHeaders: (responseHeaders, req, connInfo) => {
    responseHeaders.set("set-cookie", "sid=1234");
  },
});

editResponseHeaders

Default value: -

A function that allows to edit the response headers of all requests.

Example:

const engine = new Server({
  editResponseHeaders: (responseHeaders, req, connInfo) => {
    responseHeaders.set("my-header", "abcd");
  },
});

License

MIT